Checking a probe thermometer is easy, right?
Here are 7 ways of how NOT to check a probe thermometer
Checking temperature is an important food safety requirement, as undercooked food can lead to food poisoning. So what shouldn’t you do to ensure accurate readings? Many people use a probe thermometer although other more simple checks can be used.
1. Not “checking” (often called calibration) the thermometer regularly: Don’t just assume that the thermometer is working correctly. You need to regularly check it to ensure its accuracy. And, this could be weekly or monthly depending on its use.
To check a thermometer, immerse the end of the probe in crushed ice with a little water wait a while and note the reading, and then immerse it in pure boiling water for at least 30 seconds, ensuring it’s not too shallow or deep. The thermometer should read 0°C in the iced water or 100°C in the boiling water but you can allow 10C either side of the temperature (i.e. -10C to + 1oC and -990C to + 101oC). If it doesn’t read within these parameters try changing the battery, following the manufacturer’s instructions or you could send it to the manufacturer to adjust it, but this may be more costly than a replacement.
Do NOT check the probe at the hot end of the temperature range in the spout of a boiling kettle. This is UNSAFE and likely to lead to burns.
2. Comparing with another thermometer: Do not assume the thermometer is OK because you have compared it with another probe thermometer, as this might not be accurate. Instead, you could use a reference thermometer that is known to be accurate or check it as in step 1
3. Not verifying the range of the thermometer: Do not assume that a thermometer is appropriate for measuring all temperatures (i.e. frozen at -18oC to boiling at 100oC). Check the range of the thermometer with the manufacturer’s instructions and ensure it is suitable for the temperature range you need it for.
4. Not using an appropriate thermometer: You may need to use different types of thermometers for different types of food and cooking methods e.g. sous vide, or boiling sugar which require specific thermometers. Ensure you use the appropriate type of thermometer for what you are measuring.
For example, a digital thermometer is suitable for measuring the temperature of hot cooked foods (because you need to check the centre of the food to ensure it is at the right ‘cooked’ temperature), while an infrared thermometer can be used to measure the surface temperature of equipment and cold or frozen food as the outside is the warmest area.
5. Not waiting for the thermometer to stabilise: Insert the probe into the food, then wait for the temperature reading to stabilise. This could take a few seconds or up to 30, depending on the thermometer type. (check the manufacturers instructions)
6. Measuring temperature in the wrong part of the food: You need to measure the temperature in the thickest part of the food, as it will take the longest to heat up or cool down and the temperature will be lowest /highest here.
7. Not cleaning the thermometer properly: You must clean and disinfect a thermometer thoroughly otherwise it can lead to cross-contamination of other foods by bacteria and pathogens. Ensure the thermometer is cleaned before and after use, and between readings if used for multiple items. Ideally use different probes for cooking (which may still contain pathogens) and cooked foods.
To clean: Wash the thermometer with hot, soapy water and rinse thoroughly. You can also use a probe wipe or sanitising solution approved for food-contact surfaces.
By following the points above, you can be reassured that you are using your thermometer correctly and it’s accurate and therefore all your temperature records will be correct. A regularly checked probe is good due diligence.
Thank you for reading.
Karen Meadows of Safety in Action Ltd.
More information on food safety is found here: https://safetyinaction.co.uk/services/food-safety/
If you think I can help your business do call on 07786622741or email on info@safetyinaction.co.uk
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This blog has been written in collaboration with the AI tool, Chat-GTP.
Food Safety Consultant | Worcestershire | West Midlands | Hospitality | Food business